Unexpected occurrence of right to left shunt during lung perfusion scintigraphy: a problem-based learning exercise

This case report presents a problem-based learning exercise that occurred during lung perfusion scintigraphy with technetium-99m macroaggregated albumin (99mTc-MAA) with the incidental finding of a previously undiagnosed right-to-left shunt. The pathology manifested with a redirection of 99mTc-MAA-loaded blood into systemic circulation and subsequent uptake in gastric, renal, and thyroid tissues. Incorrect radiopharmaceutical administration, radiopharmacy error and independent constituents of 99mTc-MAA offered alternative explanations which required exclusion. Subsequent recommendations included diligent use of safety procedures and appropriate documentation during receiving, dispensing and administration of radiopharmaceuticals. Clinical suspicion of RLS may warrant additional 99mTc-MAA imaging to confirm diagnosis or quantify severity.